This commit was manufactured by cvs2svn to create tag 'buildscript'.

[IRC.git] / Robust / cup / java_cup / runtime / virtual_parse_stack.java

diff --git a/Robust/cup/java_cup/runtime/virtual_parse_stack.java b/Robust/cup/java_cup/runtime/virtual_parse_stack.java
deleted file mode 100644 (file)
index a4386aa..0000000
--- a/Robust/cup/java_cup/runtime/virtual_parse_stack.java
+++ /dev/null
@@ -1,145 +0,0 @@
-
-package java_cup.runtime;
-
-import java.util.Stack;
-
-/** This class implements a temporary or "virtual" parse stack that 
- *  replaces the top portion of the actual parse stack (the part that 
- *  has been changed by some set of operations) while maintaining its
- *  original contents.  This data structure is used when the parse needs 
- *  to "parse ahead" to determine if a given error recovery attempt will 
- *  allow the parse to continue far enough to consider it successful.  Once 
- *  success or failure of parse ahead is determined the system then 
- *  reverts to the original parse stack (which has not actually been 
- *  modified).  Since parse ahead does not execute actions, only parse
- *  state is maintained on the virtual stack, not full Symbol objects.
- *
- * @see     java_cup.runtime.lr_parser
- * @version last updated: 7/3/96
- * @author  Frank Flannery
- */
-
-public class virtual_parse_stack {
-  /*-----------------------------------------------------------*/
-  /*--- Constructor(s) ----------------------------------------*/
-  /*-----------------------------------------------------------*/
-
-  /** Constructor to build a virtual stack out of a real stack. */
-  public virtual_parse_stack(Stack shadowing_stack) throws java.lang.Exception
-    {
-      /* sanity check */
-      if (shadowing_stack == null)
-       throw new Exception(
-         "Internal parser error: attempt to create null virtual stack");
-
-      /* set up our internals */
-      real_stack = shadowing_stack;
-      vstack     = new Stack();
-      real_next  = 0;
-
-      /* get one element onto the virtual portion of the stack */
-      get_from_real();
-    }
-
-  /*-----------------------------------------------------------*/
-  /*--- (Access to) Instance Variables ------------------------*/
-  /*-----------------------------------------------------------*/
-       
-  /** The real stack that we shadow.  This is accessed when we move off
-   *  the bottom of the virtual portion of the stack, but is always left
-   *  unmodified.
-   */
-  protected Stack real_stack;
-
-  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
-
-  /** Top of stack indicator for where we leave off in the real stack.
-   *  This is measured from top of stack, so 0 would indicate that no
-   *  elements have been "moved" from the real to virtual stack. 
-   */
-  protected int real_next;
-
-  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
-
-  /** The virtual top portion of the stack.  This stack contains Integer
-   *  objects with state numbers.  This stack shadows the top portion
-   *  of the real stack within the area that has been modified (via operations
-   *  on the virtual stack).  When this portion of the stack becomes empty we 
-   *  transfer elements from the underlying stack onto this stack. 
-   */
-  protected Stack vstack;
-
-  /*-----------------------------------------------------------*/
-  /*--- General Methods ---------------------------------------*/
-  /*-----------------------------------------------------------*/
-
-  /** Transfer an element from the real to the virtual stack.  This assumes 
-   *  that the virtual stack is currently empty.  
-   */
-  protected void get_from_real()
-    {
-      Symbol stack_sym;
-
-      /* don't transfer if the real stack is empty */
-      if (real_next >= real_stack.size()) return;
-
-      /* get a copy of the first Symbol we have not transfered */
-      stack_sym = (Symbol)real_stack.elementAt(real_stack.size()-1-real_next);
-
-      /* record the transfer */
-      real_next++;
-
-      /* put the state number from the Symbol onto the virtual stack */
-      vstack.push(new Integer(stack_sym.parse_state));
-    }
-
-  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
-
-  /** Indicate whether the stack is empty. */
-  public boolean empty()
-    {
-      /* if vstack is empty then we were unable to transfer onto it and 
-        the whole thing is empty. */
-      return vstack.empty();
-    }
-
-  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
-      
-  /** Return value on the top of the stack (without popping it). */
-  public int top() throws java.lang.Exception
-    {
-      if (vstack.empty())
-       throw new Exception(
-                 "Internal parser error: top() called on empty virtual stack");
-
-      return ((Integer)vstack.peek()).intValue();
-    }
-
-  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
-
-  /** Pop the stack. */
-  public void pop() throws java.lang.Exception
-    {
-      if (vstack.empty())
-       throw new Exception(
-                 "Internal parser error: pop from empty virtual stack");
-
-      /* pop it */
-      vstack.pop();
-
-      /* if we are now empty transfer an element (if there is one) */
-      if (vstack.empty())
-        get_from_real();
-    }
-
-  /*. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*/
-
-  /** Push a state number onto the stack. */
-  public void push(int state_num)
-    {
-      vstack.push(new Integer(state_num));
-    }
-
-  /*-----------------------------------------------------------*/
-
-}